1. Field of Invention
The invention concerns a rotating helical charger for compressible media.
2. Description of Related Art
A helical charger with rotating displacement disks is disclosed in FIG. 5 of U.S. Pat. No. 3,989,422. The disclosed helical charger is characterized by conveying a gaseous working medium, comprising, for example, air on an air-fuel mixture, almost without pulsation, and can therefore be used advantageously for the charging of internal combustion engines. In the disclosed compressor, several approximately sickle shaped work spaces are arranged between helical ribs. During operation of the compressor, the spaces move from an inlet to an outlet, while their volume is constantly reduced and the pressure of the working medium correspondingly increased. In these helical chargers the quantity moved at a given volumetric compressor efficiency, together with the maximum charging pressure, are determined by the drive gear ratio, as the internal pressure ratio is fixedly determined by the helical geometry selected. If a rigid driving connection is provided between the helical compressor and the driving internal combustion engine, the charger will charge even in operating states in which charging is not required, for example under a partial load or even during idling. This could lead to a loss of efficiency and possibly to unfavorable increases in temperature, if the working medium being conveyed is expanded and returned to the inlet of the charger.
In contrast to the aforementioned charger, in a charger disclosed by U.S. Pat. No. 3,600,114, only one displacement disk is mounted on an axle journal. The second disk is connected fixedly in rotation with a drive shaft. During the rotation of the first disk, the second disk is entrained in the same rotating direction and at the same rotating velocity. In the process, the disks perform a relative motion in the form of a circular displacement.
In FIGS. 8 and 9, of U.S. Pat. No. 3,600,114, a two-speed, single stage machine is disclosed in which the two mobile displacement disks are mounted loosely on stationary eccentric axles. One of the axles is hollow so that the working medium may be passed out of the machine. At their circumference the displacement disks are provided with gear rims, engaged by a common toothed gear mounted on a drive shaft.
These multiple speed machines have the advantage that each of the displacement disks are completely balanced individually and that a more uniform conveyance almost without pulsation is possible. In addition, the radial displacement, and thus the eccentricity, between the two rotating axes is smaller than with single speed machines, resulting in lower sliding velocities between the helical ribs. In principal therefore, higher rpm's may be obtained with this type of charger.
Another variant of this working principle is shown in FIG. 5 and 6 of the aforecited reference. In this machine one of the disks is again connected with a central drive shaft. In the course of the rotation this one disk, the second disk is entrained in the same direction of rotation by means of force transfer by the helical ribs. In order to equalize the axial pressure between the work spaces created between the disks, an axially mobile annular disk tightly abutting against the rear side of one of the disks is provided. Through a pressure equalizing chamber connected with the machine outlet and by means of a flat spring, the annular disk presses the two displacement disks together. The disadvantage of this arrangement consists of the fact that the annular disk must be sealed against the housing, which may be effected at the outer circumference with a large diameter and thus high sliding velocities. Furthermore, no measure is provided to relieve the pressure equalizing chamber located between the annular disk and the housing. However, such a measure would be meaningless, as the flat spring applies a constant pressure.